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Mike, UK Car Mechanic
Category: UK Car
Satisfied Customers: 39198
Experience:  Hi, I am a Car/ vehicle technician of 34 years. 29of -running my own repair/diagnostic business.
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BMW 525i: sport..misfire..whole car runs fine

Customer Question

Hi there,
I have an 05 BMW 525D sport. Last few weeks it has a misfire in the morning and runs rough the whole car shakes until I rev it and drive about 300 yards then it runs fine. There is no MIL light or anything. I took it to a local garage last week and they thought itwas an injector so they put in a new injector and tried it on all 6 but problem remains. They now think that one of the pistons mightbe an issue and I might need to recondition them or replace the engine !!! I cant believe this is the case as the car drives fine except its down in power abit. On the diagnostics it also shows the Throttle body as an error , could this be causing the misfire ?
look forward to you expertise.
Kind regards,
Submitted: 7 years ago.
Category: UK Car
Expert:  Mike replied 7 years ago.
Hello Chris - Welcome to justanswer...

I doubt there are any problems with the pistons etc at all..

You need to check , or have checked - maybe elsewhere....the inlet manifold.

There is a known issue with these with the flaps sticking inside... worse case scenario is that they break and go in the engine and literally wreck the engine.. so as you are having such problems.. you need to have this checked out asap....and ideally by someone who has a knowledge of the subject..

Some cars had a recall on this - I know a lot of the 530's were recalled - so have a word with your local Bmw dealer...give them the VIN of the car and they will be able to tell you if the car is subject to a recall and if so, if its been done or needs to be done..

The cure was to replace the manifold - it comes out at about 330£ give or take..but the first thing to do is to speak to the dealer as I say to get the full info on your VIN / car... and then go from there...

But that is the most likely issue here ...

I Sincerely hope I have helped you - Please ask me if you need more help...

Kind Rgds, MIKE


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Customer: replied 7 years ago.

Hi Mike,

Thanks for the reply - yes we originally thought it was the swirl flaps issue aswell but he removed the manifold and they are fine.So then he thought it was the injectors and we got a new injector from Bosch - he tried this in all six positions but the problem still exists - that is why he know thinks its a piston issue.

Based on recieving a error for throttle body could this casue the issue we seeing ?


Expert:  Mike replied 7 years ago.
Hello again Chris - thank you for your reply..

My apologies that I couldn't get back to you sooner today..

Okay.. throttle body wouldn't cause cylinder specific misfire Chris.. you (they) need to find out if its is cylinder specific.. that would narrow things down altogether..

The best way to do that is with a compression test... that will tell for sure if there is a piston , cylinder or valve problem.. so that has to be the next step to ID that for sure one way or the other , then you can progress from there..

SO you need to rule out - or find any engine mechanical problems via testing as above first ..

After that - if there are none.. then there are several possibilities that would cause a misfire..
These include air in the fuel, fuel pump problems, filter... fuel rail pressure sensor, fuel rail control valve, fuel quantity adjuster - high pressure fuel pump and lastly, electrical wiring / connection problems..

There's been no mention of any proper diagnostic testing having been carried out Chris - I know there is no MIL on.. but one, make sure the MIL works as a first step.. then general fault code read should always be done regardless of MIL ..and go from there.. fault code directed if present... If none - then other, Live Data tests should be done, inc fuel pressure tests etc..

From what you have said Chris, it does sound as though none of this has been done.. It needs to be - guessing can be expensive for you... ie, replace engine.. very expensive and very much over kill at this stage..

If the garage doesn't have the equipment as above Chris - you need to move it to a garage that has - to be able to do all the testing as above...and then you will get to the bottom of it ..

You might have a piston / engine issue as they have said - but that does seem to have been a bit jumped at from what you have said they have done / not done..

Follow through on the above Chris and you will get there with it - let me know if I can help anymore at all..

Best Rgds. MIKE..


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